1. Field of the Invention
The present invention is directed to a substrate and a manufacturing method thereof, more specifically to a substrate embedded with a passive device and a method for manufacturing the substrate.
2. Description of the Related Art
Today, packaging substrates are required to improve their performance to keep up with the rapid improvement of performance of semiconductors. Printed circuit boards must essentially be denser, faster and smaller. In the areas of integrated parts, such as semiconductors and thin film devices, particularly, there is heavy research to address these needs. There has been increased demand for high-density recording as well in the area of recording medium such as the magnetic recording head.
The demand for multi-function, high-performance electronic devices necessitates the development of high-density printed circuit boards. Consequently, the demand for printed circuit boards, in which high-density packing is capable, is rapidly increasing in order to satisfy this requirement. Packing an MLCC, for example, can make the printed circuit board much thinner and the surface area much more useful, thereby realizing a higher-density printed circuit board. However, there are a number of technical obstacles in packing this kind of electronic part. It is important to secure the reliability of an electronic part during the packing process and the thermal deformation of a printed circuit board. Inhibiting the warpage of a printed circuit board, in which a hole for packing an electronic part is made, is particularly important for securing the reliability of the electronic part as well as increasing the productivity of the printed circuit board.
Moreover, the parts can be installed in the substrate in order to create space for packing highly-integrated parts. Among the parts installed in the substrate, passive devices such as the capacitor can hold a constant voltage momentarily and consequently maintain a signal formed in the circuit without distorting the signal.
FIG. 1 is a diagram showing a substrate embedded with a multilayer ceramic condenser, in accordance with the prior art. Illustrated in FIG. 1 are a core substrate 30, a through hole 32, tapers 32a, a UV tape 40, an IC chip 20, die pads 22, transition layers 38, filler 41 and press plates 100A and 100B.
A cavity is formed by drilling or laser-processing a copper clad laminate or a pre-preg such that an electronic part can be packed. The electronic part is fixed with a conductive adhesive on a copper coil and then is inserted in the copper clad laminate or pre-preg. With this method, it is not easy to prevent the warpage of the substrate and secure the reliability of the packed chip because the core material of the copper clad laminate is an epoxy type, which can cause warpage by the difference in stiffness and thermal expansion coefficient with the adhesive injected for fixing the chip. This kind of substrate warpage may apply mechanical pressure on the packed MLCC, and cause a reliability problem of the MLCC.